In recent years, imaging apparatuses including a digital still camera and a digital video camera have been designed more and more compactly in pursuit of improved portability and better user-friendliness. Accordingly, a housing of an optical system or a lens barrel employed in the imaging apparatus has been designed more and more compactly. There is still an increasing demand for higher image quality and a larger number of pixels. Even if lenses that are optical elements are made larger in size, a driving mechanism is downsized in order to realize a compact housing of an optical system.
Moreover, a so-called collapsible lens barrel employed in an imaging apparatus such as a digital still camera or a digital video camera has been requested to become more compact and thin from the viewpoint of portability and accompanying usefulness. In particular, as for the digital still camera, articles resulting from the quest for further portability and accompanying usefulness such as articles capable of being put into a chest pocket of a shirt or a pocket of jeans are winning popularity nowadays. There is therefore a great demand for a thin housing of an optical system.
The so-called collapsible lens barrel has been disclosed in Japanese Unexamined Patent Publication No. 2002-296480, and the lens driving mechanism has been disclosed in Japanese Unexamined Patent Publication No. 2002-287002. In general, a guide shaft must be highly precisely positioned and locked in order to cramp movable lenses, which are incorporated in the collapsible lens barrel or a collapsible camera, so that the lenses can be moved in optical-axis directions, while highly precisely aligning the movable lenses with one another.